About the version of blender written in bl_info
The Blender version in the bl_info should indicate the version of Blender it was written for. Future releases of Blender may change the API and the version information can be used to perform a simple check whether the add-on may work with the Blender release. Blender 2.8x already displays a warning when an add-on with blender lower than (2, 80, 0) is installed. Automatically updating the value of blender would therefore defeat its purpose.